Effects Of Phosphorus Addition And N:P Of Substrates On Fine Roots Decomposition And Enzyme Activities In Mid-subtropical Forest

Fine root decomposition is the main way to nutrient return of the forest ecosystem,is important to maintain the process system of material circulation and productivity,quality,environment and substrate by decomposing microbial factors comprehensive regulation,decomposition pattern showing a different.C.carlesii(Castanopsis carlesii)as the eastern humid subtropical typical native broad-leaved tree species in China,Chinese fir(Cunninghania lanlancceolata)needle timber species endemic to China's speed,previously on the soil P lower effectiveness of Sanming forest ecosystem and global change research station of the nature reserve of Castanopsis kawakamii natural forest of Castanopsis carlesii do the decomposition of research,research found that P(Phosphorus)with high content of C.carlesii fine root decomposition faster than the addition of P promotes the fine root,fine root decomposition,P is one of the main factors affecting the area of fine root decomposition.In order to further clarify the regulatory mechanisms of P in middle subtropical zone of fine root decomposition in this paper,the dative's sample(from 5 adjacent Castanopsis km)but higher soil available P Sanming Ninghua Swan cave preserve natural forest for field experiment plots of exogenous P four gradient(high phosphorus HP,phosphorus MP LP,CT,low phosphorus control)add further observation the two root and mixed during fine roots decomposition loss of dry matter,root nutrient,chemical composition and decomposition of dynamic main function decomposition enzyme activity,and increased monitoring of the decomposition period pH,soil nutrient and enzyme activity dynamic.The indoor control experiments,the decomposition of more than three kinds of fine roots in nutrient quartz sand,and set the control and add to P interference processing,strong adsorption and removal phosphorus acid red soil added foreign source,further confirmed that endogenous or exogenous(substrate)(environment)on the decomposition of nutrients the decoupling limit,substrate and soil P availability effect on fine root decomposition,to provide a reference for the study of forest management and management.Experimental results show as below:(1)Decomposition in the wild for 2 years period,the fine root decomposition are showed a trend of slow down after the C.carlesii fine root dry weight residual rate was significantly lower than that of Chinese fir(P<0.05).The different decomposition of fine roots dry weight loss rate showed exponential decay process(Table 3.1),use Olson model to obtain the C.carlesii,mixing and fine root decomposition coefficient K field size were MP(0.315)>HP(0.285)>LP(0.260)>CT(0.215),MP(0.206)>HP(0.193)>LP(0.184)>CT(0.150)and HP(0.271)>LP(0.239)>MP(0.182)>CT(0.165).The addition of P increased the decomposition rate of fine roots,promoted the decomposition of fine roots,but promoted the fine root of Chinese Fir with lower P content.However,it did not appear to accelerate with the increase of P levels.It's fine root decomposition of Castanopsis dative are similar,the difference is the study area soil P availability is high,compared to only HP treated Chinese fir root decomposition rate is faster,the other treatments were not root decomposition rates higher,may Ninghua plots lower temperature caused by the regulation that the decomposition temperature factor,even more than soil nutrient availability is a greater impact.(2)2 years in the xwilderness decomposition period,soil pH three during fine roots decomposition value was up-down-up-down(double peak type)change trend,and reached the peak in the summer and autumn heat in the same quarter,showing seasonal change.Fine root decomposition can increase soil pH value,and the decomposition of fine root of coniferous tree has the greatest effect on the improvement of soil pH.Compared with the control,the addition of exogenous P significantly reduced soil pH and caused soil acidification,which was greater than the decomposition of fine roots.(3)2 years in the wilderness decomposition period,soil N concentrations of the three kinds of treatment during fine roots decomposition and then decreased,the maximum soil N concentration increase C.carlesii during fine roots decomposition,followed by mixed fine roots of Chinese fir,the smallest,but the overall decomposition effect on soil N concentration is very small,P the effects of different treatments was not significant,with the decomposition time vary.The soil P concentration showed an upward trend,but the concentration of P in the three fine roots decomposed by CT did not increase very much.The addition of P significantly increased the soil P concentration and increased with the increase of P level.Key words:mid-subtropical;phosphorus;fine root;decomposition;enzymatic activity;nutrient release.(4)In the 2 year decomposition period,the N concentration of different fine roots all showed an upward trend,and the residual rate of fine root N was more than 100%,showing a pattern of net enrichment.P addition increased the fine root N concentration,but the difference between treatments was not significant.The three fine root P concentrations showed a downward trend and showed a pattern of release under CT treatment.The addition of P increased the concentration of fine root P and showed a pattern of accumulation and release.The relative root types,the effect of P addition on the fine root P concentration is larger,which can effectively improve the root P concentration,the maximum increase of P initial concentration of fine roots of Chinese Fir with low P content,low P content that the initial decomposition of fine roots demand for P is higher.(5)2 years of field decomposition period,the treatment of three kinds of fine roots can extract and cellulose concentration generally increased first and then decreased,the lignin concentration increased slowly,reflecting the roots at the early stage of the decomposition of cellulose within short time is difficult to decompose,and the decomposition of lignin is mainly affected by the late limit.The addition of P decreased the concentration of extractable and lignin,which could effectively promote lignin degradation and accelerate the loss of soluble substances during the leaching stage.(6)2 years in the wilderness decomposition period,soil enzyme activity of each treatment during fine roots decomposition of seasonal variation is obvious,fine root decomposition enzyme activity was significantly greater than that of soil enzyme activity(P<0.01),different decomposition of fine roots have different effects on soil enzyme activity.But on the whole,four kinds of Main Soil Hydrolase cellulose degradation and root of acid phosphatase(AP),beta-N-Acetylglucosaminidase(NAG),beta glucosidase(beta G)and cellulose hydrolase(CBH)was first increased and then decreased,while the two main points of lignin solution the oxidase:phenol oxidase(PhOx)and peroxidase(PerOx)activity was increased.P addition significantly decreased AP activity and accumulation value(P<0.01)in soil and fine roots,and increased the activities of beta G,CBH,NAG,PhOx and PerOx and their accumulation,and MP treatment enhanced the maximum.P and add different degree increased the total accumulation of roots and soil enzyme activity in the decomposition process,the performance of the MP>LP>HP>CT,show that the addition of P may enhance the overall strength of soil microbial activity,thus affecting the fine root decomposition enzyme secretion,but not with the addition of P increased the level of.The decomposition of regional decomposition enzyme activity and enzyme activity of each root total cumulative value was less than c.kawakamii plots,this may be the cause of one of the main reasons of the slow decomposition.(7)Field decomposition were similar in different period of indoor decomposition of fine root decomposition was also slow down after the trend,adding P promoted the decomposition of fine roots of Chinese fir,the low P content on root promoting effect is stronger,but the overall root decomposition rates than wild fast,that the decomposition and temperature control of water the most suitable substrate is more conducive to root.In the process of decomposition and indoor chemical group N,P,and fine root decomposition enzyme and field decomposition rules are similar,the difference is the root of four kinds of enzymes at the early stage of the decomposition(0-42 days)were decreased after the rise,may again with the stage number of fungus breeding students,but mainly by decomposition the substrate quality control,exogenous P treatment can change with fine root N,P and chemical component concentration and the number of decomposition enzymes secretions so as to effectively promote the region's fine root decomposition.The mutual validation of indoor and field decomposition studies can better reveal the response of fine root decomposition of subtropical forests to P.